1. Field
The invention relates to adhesive compositions for bonding substrates, and more particularly to adhesive compositions including a curable resin component, a curing agent, and a conductive filler material. The adhesive compositions exhibit excellent thermal conductivity and can be easily and cleanly dispensed, particularly in die attach applications for the micro-electronics industry.
2. Related Technology
Adhesive compositions play a prominent role in many industrial applications. For example, in the micro-electronics industry, packaging engineers faced with increased challenges of finding new and better ways of creating and attaching dies often rely on adhesive compositions to secure semiconductor chips to a circuit board or other substrate during the die attach process. In particular, as micro-electronic devices, such as semiconductor packages, have become smaller and more powerful, the micro-electronic packaging industry has started to stack multiple semiconductor die into the same package to increase circuit density without increasing the total area of the circuit board which is occupied.
In order to obtain better performance of electrical components, including these stacked die packages, the adhesive bond line interface between the components needs to be very thin while still maintaining superior adhesive strength and high thermal and electrical conductivity to avoid the reduced reliability, slower performance, and reduced power-handling capacity that can result from heat and electrical buildup. The resin bleed often leads to unreliable performance. In addition, the rheology of the adhesive composition should allow for the rapid dispensing of individual units, or dots, of adhesive of predicable size and shape.
Thermally conductive adhesives have been an important interface material in semiconductor die attach technology. Especially important are adhesives that are fluid during application and can penetrate interfacial or surface voids, effectively lowering interfacial thermal and electrical resistance.
The thermal conductivity of these adhesives may be improved by the addition of a conductive filler material to the resin matrix. For example, U.S. Pat. No. 4,147,669 (Shaheen) discloses an adhesive matrix with a filler material comprised of gallium, aluminum, gold, copper, or silver in a resin. U.S. Pat. No. 6,500,891 (Kropp et al.) describes a thermally conductive adhesive including a resin mixed with a filler material which includes spherical alumina particles. However, because these filler materials are naturally abrasive, including the high amount of filler material within the resin matrix necessary to obtain the desired conductivity properties makes it difficult to dispense the adhesive into tight spaces using a needle tip with the rate and consistency necessary in high-speed dispensing systems.